1. Field of the Invention
This invention relates broadly to the field of modems and in particular to modems that can switch between voice and data communications.
2. Description of the Prior Art
Modems are used to communicate digital information from one data terminal device to another via a telephone line. As the modem is being used to transmit data via the telephone line, a need may arise to use the telephone line for voice communication. Therefore, it is an important feature of modems for the user to be able to interrupt data communications for purposes of making a voice call.
Other modem systems have been used to switch between voice and data communications, but they have required complex commands from the users to the modems and between modems. Under one approach, the user switches from data to voice by sending code between his local modem and the remote modem and switching the handset on or off under modem control. Under a second approach, a speaker is used at the remote modem with a timer, but the speaker and timer are enabled and disabled only after a complex series of commands by the user to the local modem before and after, respectively, the voice portion of the communication.
Both of these prior systems are more complex than an ordinary voice call where the user simply picks up the telephone handset. The present invention overcomes this drawback for switching back and forth between data and voice communications.